We will determine whether the chromatin of yeast cells undergoing meiosis and recombination differs, at the level of the nucleosome, from vegetative chromatin. The properties to be investigated include sensitivity to various nucleases, such as staphylococcal and DNAse I, the products of digestion with such nucleases, and the binding isotherm of ethidium bromide. The histones from mitotically growing yeast will be compared with those from meiotic chromatin. We will look for differing patterns of phosphorylation and acetylation in the two states. We will also determine whether there are new, meiosis-specific histones synthesized. From these data we hope to decide whether recombination involves drastic changes in the structure of eukaryotic chromatin.